一 .逗号用于并列成分之间.如果并列成分只有两个,且已有连词连接,则不须再用逗号连接；但三个或三个以上的并列成分之间,除最后两个并列成分用连词连接外,其余均须用逗号隔开.如：
1.On Saturday afternoon,Mrs Green went to the market,_______ some bananas and visited her cousin.
A.bought B.buying C.to buy D.buy
析：答案为 A 项.句中三个谓语动词相连,时态一致,属“ A,B and C ”句型.
2.The purpose of new technologies is to make life easier,_______ it more difficult.
A.not make B.not to make C.not making D.do not make
析：答案为 B 项.句中的两个不定式短语作表语,其间并无连词连接,这时第二个不定式符号 to 应保留,且第二个不定式前要用逗号与主句隔开,以区分表示目的的不定式.
二 .逗号用于同位语、定语与句子的其他部分之间.如：
3.Greenland,_______ island in the world,covers over two million square kilometres.
A.it is the largest B.that is the largest
C.is the largest D.the largest
析：答案为 D 项.句中 Greenland 后面逗号的部分,在没有连词的情况下不可为 A 项的分句； B 项因 that 不能引导非限制性定语从句而被排除； C 项因缺少引导非限制性定语从句的关系代词 which 而被排除.句中 the largest island in the world 作 Greenland 的同位语.
4.The Olympic Games _______ in 776 BC,did not include women players until 1912.
A.first playing B.to be first played
C.first played D.to be first playing
析：答案为 C 项.句中两逗号之间是过去分词短语作后置定语,相当于非限制性定语从句 which was first played…… ,强调动作的被动,并且表明该动作在说话时已经完成.
三 .逗号用于作状语的分词短语前后.如：
5.European football is played in 80 countries,_______ it the most popular sport in the world.
A.making B.makes
C.made D.to make
析：答案为 A 项.若选 B 项或 C 项,句子就会因缺少连词或主语而被排除.逗号在英语中不是并列连词,所以其前面的结构如果是主句,则其后面的就应是从句或短语.A 项和 D 项分别为现在分词与不定式,都可以作状语,但不定式作状语置于句尾时,除句中有插入成分,一般不用逗号隔开,故只能选 A 项.
四 .逗号用于 with 的复合结构与主句之间.如：
6._______ production up by 60%,the company has had another excellent year.
A.As B.For C.With D.Through
析：答案为 C 项.with 的复合结构作状语且置于句首时,其后通常要用逗号与主句隔开.
五 .逗号用于非限制性定语从句的前后.如：
7.Carol said that the work would be done by October,_______ personally I doubt very much.
A.it B.that C.when D.which
析：答案为 D 项.英语中,非限制性定语从句通常要与主句用逗号隔开,which 引导的非限制性定语从句通常要置于句尾,起补充说明的作用.
六 .逗号用于置于句首的状语从句后；但从句置后时,也可用逗号与主句隔开.如：
8._______,Mother will wait for him to have dinner together.
A.However late is he B.However he is late
C.However is he late D.However late he is